1. Field of the Invention
The present invention relates to an apparatus for plasma treatment which performs the etching, ashing, CVD treatment, ion implementation, etc. of a semiconductor wafer, glass substrate, etc.
2. Description of the Related Art
In a conventional apparatus for plasma treatment, a gas introduction device is provided over a plasma treatment chamber. A gas introduced from this gas introduction device is converted into a plasma by a coil electrode wound around the periphery of the plasma treatment chamber and this gas which has been converted into a plasma reaches a workpiece placed in the lower part of the plasma treatment chamber and is used for the plasma treatment of the object of treatment.
In recent years, the diameter of a workpiece has increased and the diameter of a plasma generation chamber in an apparatus for plasma treatment has also increased accordingly. For this reason, because the velocity of a gas for plasma generation decreases and the uniformity of plasma distribution in the plasma generation chamber worsens, the in-plane uniformity of the plasma for the workpiece also worsens or the plasma may sometimes disappear without reaching the workpiece. As a result, the treatment speed decreases.
An increase in the volume of an introduced gas is proposed in order to eliminate the above-described disadvantage. However, a larger vacuum pump for evacuation becomes necessary for increasing the volume of an introduced gas, and a more powerful high-frequency power supply becomes necessary for converting the increased gas into a plasma. This eventually leads to the consumption of large amounts of gas and electric power and a decrease in efficiency. At the same time, in actuality the size of the apparatus as a whole increases. Accordingly, it is difficult to put this idea into practical use.
Therefore, the object of the invention is to provide an apparatus for plasma treatment capable of treating a workpiece with good efficiency without the need to increase the size of the apparatus as a whole.
In order to solve the above-described problem, in the invention there is provided an apparatus for plasma treatment which comprises: an outer chamber for plasma generation connected to a gas introduction portion for plasma generation;
a coil for plasma generation provided along the periphery of the outer chamber for plasma generation; and a treatment chamber arranged below the outer chamber for plasma generation. In this plasma treatment apparatus,
within the above-described outer chamber for plasma generation, an inner chamber having a cross-sectional area smaller than that of the above-described outer chamber for plasma generation is provided coaxially with the above-described outer chamber for plasma generation.
In the invention, by coaxially installing, for example, an inner chamber inside the outer chamber, the volume between the inside of the outer chamber and the outside of the inner chamber becomes a plasma generation zone. That is, even when the size of the outer chamber for plasma generation increases, the plasma generation zone does not increase, with the result that a generated plasma can reach the workpiece while keeping the uniformity of distribution within the outer chamber even if the volume of the introduced gas is not increased.